It's becoming more taboo to use vacation time at work, and millennials may be to blame (because, of course).

According to a recent study by Project Time Off, added pressure felt by some American workers has given rise to the "work martyr."

Find out what a work martyr is and who they likely are in the slideshow above. To read Project Time Off's full report, click here.

Work martyrs are characterized as workers who find it too difficult to take a vacation because of pressure to solidify their position at work, believe only they can do their job, or feel guilty for taking time off.

Among the groups of workers most likely to be this type of worker, millennials are at the top of the list.

"The popular cultural narrative is that millennials are entitled and spoiled, expecting to be handed achievements rather than working for them," the report said. "Not only do the survey findings run counter to this narrative, this stereotype ignores the circumstances of the millennial experience which helps explain why they are most susceptible to work martyr thinking."

Millennials were also found to be most likely to value being a work martyr, have the shortest tenure at companies, and shame others for taking vacation above all other generations.

In the cause of why millennials likely don't take time off, uncertainty and fear played a role, according to the study.

"Feelings of uncertainty and disapproval are translating to more forfeited vacation time—days that cannot be rolled over, banked for later use, or cashed out," the report said. "Millennials are the most likely generation to forfeit time off, even though they earn the least amount of vacation days."

And like other generations, one fear is the mountain of work possibly waiting for them when they return, the study added.

In any case, the mindset of work martyr is hazardous to the health of workers and companies.

"The work martyr mindset is fundamentally flawed and poisonous to company cultures," the repost stated. "The negative results of such thinking should be presented to work martyrs so that they may reconsider their approach to time off."